Biological field and laboratory methods for measuring the quality of ...

BIOLOGICAL METHODS
Because of the small area sampled, data from
corin g devices are likely to provide very
imprecise estimates of the standing crop of
macrobenthos. As the data in Table 3 illustrate,
the variability in numbers of oligochaetes (a
dominant component of the fauna studied)
collected in corers is similar to that for grab-type
devices; however, the corer data were calculated
from two to three times as many replicate
samples and were collected from a relatively
homogeneous substrate.
Such additional replication with corers is
feasible because of the small amount of material
per sample that must be handled in the
laboratory. Multiple-head corers have been used
in an attempt to reduce the field sampling effort
that must be expended to collect large series of
core samples (19).
The Dendy inverting sampler (57) is a highly
efficient coring-type device used for sampling at
depths to 2 or 3 meters in nonvegetated substrates
ranging from soft muds through coarse
sand. Because of the small surface area sampled,
data obtained by this sampler suffer from the
same lack of precision (51) as the coring devices
described above. Since the per-sample processing
time is reduced, as with the corers, large series of
replicates can be collected. The Dendy sampler
is highly recommended for use in habitats for
which it is suitable.
Stovepipe-type devices include the Wilding
sampler (2, 57) and any tubular material such as
60 to 75 cm sections of standard l7-cmdiameter
stovepipe (51) or 75 cm sections of
30-cm-diameter aluminum irrigation pipe fitted
with handles. In use, the irrigation pipe or commercial
stovepipe is manually forced into the
substrate, after which the contained vegetation
and coarse substrate materials are removed by
hand. The remaining materials are repeatedly
stirred into suspension, removed with a longhandled
dipper, and poured through a woodenframed
floating sieve. Because of the laborious
and repetitive process of stirring, dipping, and
sieving large volumes of material, the collection
of a sample often requires 20 to 30 minutes.
The use of stovepipe samplers is limited to
standing or slowly moving waters having a
maximum depth of less than 60 cm. Since
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problems relating to depth of sediment penetration,
changes in cross-sectional area with depth
of penetration, and escapement of organisms are
circumvented by stovepipe samplers, they are
recommended for quantitative sampling in all
shallow water benthic habitats. They probably
represent the only quantitative device suitable
for sampling shallow-water habitats containing
stands of rooted vascular plants and will collect
organisms inhabiting the vegetative substrates as
well as those living in sediments. The coefficients
of variation for the stovepipe samples in
Table 3 are comparable to the coefficients for
grab samples, although the stovepipe samples
were collected in heavily vegetated and consequently
highly variable habitats.
3.3.4 Artificial substrates
The basic multiple-plate sampler (23) and
rock-filled basket sampler (21) have been
modified by numerous workers (17, 40) and are
widely used for investigating the macroinvertebrate
community. Both samplers may be
suspended from a surface float or may be
modified for use in shallow streams by placing
them on a rod that is driven into the stream
bottom or anchored in a piece of concrete (24).
A multiple-plate sampler similar to that
described by Fullner (17), except with circular
plates and spacers, is recommended for use by
EPA biologists. This sampler is constructed of
0.3-cm tempered hardboard cut into 7.5-cm
diameter circular plates and 2.5-cm circular
spacers. A total of 14 plates and 24 spacers are
required for each sampler. The hardboard plates
and spacers are placed on a Y4-inch (0.625 cm)
eyebolt so that there are eight single spaces, one
double space, two triple spaces, and two
quadrupIe spaces between the plates. This
sampler has an effective surface area (excluding
the bolt) of 0.13 square meter and conveniently
fits into a wide-mouth glass or plastic jar for
shipment and storage. Caution should be
exercised in the reuse of samplers that may have
been subjected to contamination by toxicants,
oils, etc.
The rock basket sampler is a highly effective
device for studying the macroinvertebrate
community. A cylindrical, chromeplated basket